Secondary batteries have attracted considerable attention as an energy source for electric vehicles and hybrid electric vehicles, which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuel. In addition, the secondary batteries have started to be used as a main component of a power storage device. Therefore, the secondary batteries are being applied to an increasing number of applications owing to advantages thereof and, in the future, the secondary batteries are expected to be applied to even more applications and products.
As applications and products, to which the secondary batteries are applicable, are increased, kinds of batteries are also increased such that the batteries can provide outputs and capacities corresponding to the various applications and products. In addition, there is a strong need to reduce the size and weight of the batteries applied to the corresponding applications and products.
For example, small-sized mobile devices, such as a mobile phone, a personal digital assistant (PDA), a digital camera, and a laptop computer, use one or several small-sized, lightweight battery cells for each device according to the reduction in size and weight of the corresponding products. On the other hand, middle or large-sized devices, such as an electric vehicle, a hybrid electric vehicle, and a power storage device, use a middle or large-sized battery module or battery pack having a plurality of battery cells electrically connected with each other because high output and large capacity are necessary for the middle or large-sized devices. The size and weight of a battery module is directly related to an accommodation space and output of a corresponding middle or large-sized device. For this reason, manufacturers are trying to manufacture small-sized, lightweight battery modules.
Meanwhile, a conventional middle or large-sized battery module is manufactured by stacking a plurality of unit bodies, adding fixing plates to the top and the bottom of the stack of the unit bodies to fix the unit bodies, and fixing the stack of the unit bodies in a frame. In this case, however, overall volume of the battery module is increased. In addition, in a case in which an individual plate is provided to fix each of the unit bodies, overall rigidity of the battery module is reduced. For this reason, it is necessary to provide an additional reinforcing member. Furthermore, in a case in which an additional cooling channel or a cooling member is further loaded for cooling the battery module, the number of parts constituting the battery module is increased and it is difficult to efficiently perform works in a limited space.
Therefore, there is a high necessity for technology that is capable of fundamentally solving the above problems.